Light sheet fluorescence microscopic imaging for the primary breakup of diesel and gasoline sprays with real-world fuels

Abstract

This paper describes the adaptation of the laser-induced fluorescence measurement technique for the investigation of the primary breakup of modern diesel and gasoline direct injection sprays. To investigate the primary breakup, a microscopic technique is required, and with the help of special tracer dyes, a high fluorescence signal can be achieved in the visible range of the electromagnetic spectrum, resulting in good image quality with a nonintensified camera. Besides the optimization of the optical setup for the microscopic field of view, different tracer dyes are compared, and their solubility and fluorescence are tested in the desired surrogate and real-world fuels. As a tracer, the phenoxazine dye Nile Red was found to provide sufficient solubility in alkanes as well as suitable emission and excitation spectrum for the use of the second-harmonic frequency of a Nd:YAG laser (532 nm). The good quantum efficiency delivered by Nile Red also meant that single-shot images clearly showing spray structures in regions measuring up to 3 mm by 3 mm around the nozzle outlet could be recorded. Compared to relatively easy shadowgraph techniques and complex and costly x-ray synchrotron measurements, light sheet fluorescence microscopic imaging is not overly complex yet delivers excellent data on spray structures as well as qualitative fuel distribution.

Investigation of Five Organic Dyes in Ethanol and Butanol for Two-Color Laser-Induced Fluorescence Ratio Thermometry

“…All measurements were performed in the linear regime of fluorescence and the dye concentrations (see Table 1) were chosen to have sufficient fluorescence intensity required for future 2c-LIF (two-color laser-induced fluorescence) thermometry of droplets in ethanol and butanol sprays [41,42]. Note that compared to dye concentration for the thermometry of liquid solutions in a test cell, atomizing sprays or single droplet studies require a relatively higher dye concentration (for better signal to noise ratio) [43,44], especially in two-dye approaches using FL [19]. Figure 3 shows the absorbance spectra of FL in (a), EY in (b), RhB in (c), Rh6G in (d), and SRh101 in (e) mixed with ethanol and butanol.…”

A Novel Approach for Measurement of Composition and Temperature of N-Decane/Butanol Blends Using Two-Color Laser-Induced Fluorescence of Nile Red

“…The well-characterized fluorescence dye Eosin Y was utilized in earlier PDS studies [ 2 , 15 , 20 , 23 , 24 , 25 ] in ethanol and butanol sprays, but it is not soluble in alkanes. The tracer nile red (C 20 H 18 N 2 O 2 ) is commonly applied in the field of microfluidic systems and biology [ 26 , 27 ] and is also a suitable tracer for alkanes [ 28 , 29 ]. Nile red is a suitable tracer for PDS in alkanes due to its low temperature dependency at moderate ambient conditions.…”

Planar droplet sizing for studying the influence of ethanol admixture on the spray structure of gasoline sprays

“…Many investigations on droplet sizing using LIF/Mie ratio in alcohol or water sprays already exist in the literature (Koegl et al 2018b(Koegl et al ,c, 2019aMishra et al 2014Mishra et al , 2017Mishra et al , 2019Storch et al 2016b). The tracer Eosin Y, which was mainly used in the previous studies, is not soluble in alkanes or gasoline fuels (Durst et al 2018). The tracer options for alkanes, oils and gasoline are more limited…”